Metabolic syndrome and insulin resistance in subjects with morbid obesity

Background & Aims There is evidence that a group of subjects with obesity fits the characteristics of metabolically healthy, but obese population. We aimed to assess the prevalence of the metabolic syndrome (MS) in non-diabetic subjects with morbid obesity (BMI ≥ 40 Kg/m2), and its correlation with insulin resistance. Methods We analyzed the data of 211 patients (55 males, 156 females) with morbid obesity and without overt diabetes, consecutive referred for weight loss management. All subjects underwent an oral glucose tolerance test, and insulin resistance was calculated by the Homeostasis Model Assessment (HOMA) at baseline and by the Oral Glucose Insulin Sensitivity (OGIS) during the glucose and insulin curve. Clinical and biochemical features of MS were also determined. Results The criteria for MS were fulfilled in 74% of cases, and 10 patients had obesity as the sole feature. HOMA-R was normal in 26% of cases, whereas OGIS was normal only in 3 females. HOMA-R and OGIS significantly differed in relation to the presence of MS, and a trend was observed in both tests as function of the number of factors of MS (P<0.001). At logistic regression analysis, after adjustment for age, sex, BMI at age 20 years, present BMI and waist circumference, OGIS was the only parameter of insulin resistance significantly associated with MS (Odds Ratio, 2.42; 95% confidence interval, 1.63–3.60). Conclusions A small number of metabolically healthy, but obese cases exists also in the subgroup of patients with morbid obesity, in whom insulin resistance maintains its pivotal role.